The invention relates to a pigment preparation in which a platelet-shaped nacreous pigment is coated with a polymer resin and, if appropriate, plasticizers, solvents and surfactants.
Because of their platelet-shaped structure, nacreous pigments cannot be dispersed like conventional pigments under the action of highshearing forces, since the pigment platelets are thereby crushed and the nacreous luster is thus reduced or even destroyed completely.
Various attempts have therefore been made to solve the problem of incorporation of nacreous pigments, in particular into thermoplastics. Bismuth oxychloride and basic lead carbonate are therefore as a rule used in the already pre-dispersed form as a paste. In the case of metal oxide/mica pigments, however, such pastes can be prepared only with up to a maximum of 40-45% by weight of pigment.
It is known from German Offenlegungsschrift No. 2,603,211 that the pigment particles can be brought into a pre-dispersed form by encasing in a solid polymer which dissolves in the medium in which the pigment is to be dispersed. This casing must be applied, however, in a relatively complicated process.
A liquid adhesive with which the polymer granules are wet before being mixed with a pulverulent nacreous pigment is known from German Offenlegungsschrift No. 3,221,044. However, only the problems which arise during coloring of plastic in granule form are solved by this process, and the process is still too complicated for the user.